Polyethylene is the material thatis used in various sectors of the economy. Products from it are also used in everyday life. The usual polyethylene retains its strength to a temperature of 130 degrees. However, often it is necessary to use this material under more severe conditions, with a higher temperature regime and pressure, for example, in heating and hot water supply systems.
This need led to the search for ways toobtaining a more durable material. The technology found made it possible to obtain cross-linked polyethylene, which has a greater molecular weight than the conventional material and has improved characteristics. By stitching is understood the process in which the links of molecules due to the formation of transverse bonds are connected in a three-dimensional wide-mesh net.
Depending on the applied effectdistinguish between chemical and physical. In the latter case, pipes (cross-linked polyethylene used to create these products) are irradiated with X-ray hard rays. This technology is very productive, and in a minute you can get up to 80 meters of material.
The disadvantage of the method lies in the fact that the crosslinkedPolyethylene has a non-uniformity in the thickness of the pipe. At the inner side, the lowest percentage of the molecules is obtained, while in the outer side, the highest is obtained.
When using the chemical method forsubstitution of hydrogen atoms in molecules use a special substance silane. Accordingly, a silane crosslinked polyethylene is produced. Pipes during production pass through a special bath filled with a substance. That allows to make uniform the process of cross-linking from the inner and outer surfaces deep into the walls of the pipe. This technology makes it possible to obtain pipes with a high percentage of processing, and the material is designated PEH-B.
There is a procedure for processing polyethylene with nitric radicals, the resulting material is labeled PEH-D. However, this technology is not used because of low efficiency.
Also perform crosslinking with peroxides.In this case, the manufacturing process involves mixing the peroxide and polyethylene, after which a cross-linked polyethylene of the PEH-A group is obtained in the molten state and under the influence of high temperature.
Pipes from materials (groups B, C) are used for water supply and heating, however, they have a number of limitations, which are related to the strength and plasticity of products.
The most successful pipes are made of Group A polyethylene, they have high fatigue strength, crack resistance, shape stability, flexibility, endurance to impacts.
Cross-linked polyethylene heating pipesare used for individual, civil and industrial construction. With their help they carry out floor-to-ceiling radiator wiring and create underfloor heating systems.
